From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- Documentation/driver-api/rfkill.rst | 132 ++++++++++++++++++++++++++++++++++++ 1 file changed, 132 insertions(+) create mode 100644 Documentation/driver-api/rfkill.rst (limited to 'Documentation/driver-api/rfkill.rst') diff --git a/Documentation/driver-api/rfkill.rst b/Documentation/driver-api/rfkill.rst new file mode 100644 index 000000000..7d3684e81 --- /dev/null +++ b/Documentation/driver-api/rfkill.rst @@ -0,0 +1,132 @@ +=============================== +rfkill - RF kill switch support +=============================== + + +.. contents:: + :depth: 2 + +Introduction +============ + +The rfkill subsystem provides a generic interface for disabling any radio +transmitter in the system. When a transmitter is blocked, it shall not +radiate any power. + +The subsystem also provides the ability to react on button presses and +disable all transmitters of a certain type (or all). This is intended for +situations where transmitters need to be turned off, for example on +aircraft. + +The rfkill subsystem has a concept of "hard" and "soft" block, which +differ little in their meaning (block == transmitters off) but rather in +whether they can be changed or not: + + - hard block + read-only radio block that cannot be overridden by software + + - soft block + writable radio block (need not be readable) that is set by + the system software. + +The rfkill subsystem has two parameters, rfkill.default_state and +rfkill.master_switch_mode, which are documented in +admin-guide/kernel-parameters.rst. + + +Implementation details +====================== + +The rfkill subsystem is composed of three main components: + + * the rfkill core, + * the deprecated rfkill-input module (an input layer handler, being + replaced by userspace policy code) and + * the rfkill drivers. + +The rfkill core provides API for kernel drivers to register their radio +transmitter with the kernel, methods for turning it on and off, and letting +the system know about hardware-disabled states that may be implemented on +the device. + +The rfkill core code also notifies userspace of state changes, and provides +ways for userspace to query the current states. See the "Userspace support" +section below. + +When the device is hard-blocked (either by a call to rfkill_set_hw_state() +or from query_hw_block), set_block() will be invoked for additional software +block, but drivers can ignore the method call since they can use the return +value of the function rfkill_set_hw_state() to sync the software state +instead of keeping track of calls to set_block(). In fact, drivers should +use the return value of rfkill_set_hw_state() unless the hardware actually +keeps track of soft and hard block separately. + + +Kernel API +========== + +Drivers for radio transmitters normally implement an rfkill driver. + +Platform drivers might implement input devices if the rfkill button is just +that, a button. If that button influences the hardware then you need to +implement an rfkill driver instead. This also applies if the platform provides +a way to turn on/off the transmitter(s). + +For some platforms, it is possible that the hardware state changes during +suspend/hibernation, in which case it will be necessary to update the rfkill +core with the current state at resume time. + +To create an rfkill driver, driver's Kconfig needs to have:: + + depends on RFKILL || !RFKILL + +to ensure the driver cannot be built-in when rfkill is modular. The !RFKILL +case allows the driver to be built when rfkill is not configured, in which +case all rfkill API can still be used but will be provided by static inlines +which compile to almost nothing. + +Calling rfkill_set_hw_state() when a state change happens is required from +rfkill drivers that control devices that can be hard-blocked unless they also +assign the poll_hw_block() callback (then the rfkill core will poll the +device). Don't do this unless you cannot get the event in any other way. + +rfkill provides per-switch LED triggers, which can be used to drive LEDs +according to the switch state (LED_FULL when blocked, LED_OFF otherwise). + + +Userspace support +================= + +The recommended userspace interface to use is /dev/rfkill, which is a misc +character device that allows userspace to obtain and set the state of rfkill +devices and sets of devices. It also notifies userspace about device addition +and removal. The API is a simple read/write API that is defined in +linux/rfkill.h, with one ioctl that allows turning off the deprecated input +handler in the kernel for the transition period. + +Except for the one ioctl, communication with the kernel is done via read() +and write() of instances of 'struct rfkill_event'. In this structure, the +soft and hard block are properly separated (unlike sysfs, see below) and +userspace is able to get a consistent snapshot of all rfkill devices in the +system. Also, it is possible to switch all rfkill drivers (or all drivers of +a specified type) into a state which also updates the default state for +hotplugged devices. + +After an application opens /dev/rfkill, it can read the current state of all +devices. Changes can be obtained by either polling the descriptor for +hotplug or state change events or by listening for uevents emitted by the +rfkill core framework. + +Additionally, each rfkill device is registered in sysfs and emits uevents. + +rfkill devices issue uevents (with an action of "change"), with the following +environment variables set:: + + RFKILL_NAME + RFKILL_STATE + RFKILL_TYPE + +The content of these variables corresponds to the "name", "state" and +"type" sysfs files explained above. + +For further details consult Documentation/ABI/stable/sysfs-class-rfkill. -- cgit v1.3.1